The present invention relates to a hot water supplying device capable of supplying a predetermined amount of hot water to which the hot water is needed, and more particularly, it relates to a hot water supplying device most suitable for the automatic coffee vending machines.
The automatic coffee vending machine needs the hot water supplying device to make liquid coffee. The conventional hot water supplying device of this type comprises a tank into which water is introduced, a heater for heating the water in the tank, and a pump for feeding the water in the tank, which has been heated to a predetermined temperature by the heater. In the case of this conventional hot water supplying device, however, it was impossible to successively and repeatedly supply a predetermined amount of hot water having a temperature of about 100.degree. C. and needed to make liquid coffee. This is because the temperature range of hot water allowed through the usual pressure pump was limited to lower than about 90.degree. C.
Even when a pressure pump which can be used to pressure feed hot water of 100.degree. C. is provided, the conventional hot water supplying device has the following drawbacks. A large amount of hot water must be stored in the tank to make it possible to successively supply a certain amount of hot water from the tank. An extremely large-sized and strong heater is therefore needed to heat speedily the large amount of water introduced into the tank due to supply the large amount of hot water from the tank, and to keep it hot. In this case, however, power consumed by the heater greatly increases, thereby making a cup of coffee vended by the machine expensive. In addition, the power supply source is practically a commercial one, thereby making it almost impossible to use the commercial power supply source for such large-sized and strong heater.